The intense scientific and technological collaboration between a group of scientists and engineers coming from ELI Beamlines (IoP-ASCR, Prague), Service des Basses Températures (INAC-CEA, Grenoble) and PALS (IPP-ASCR, Prague) has led to the world’s first experimental test of a cryogenic targetry delivering system, made of a very thin solid hydrogen ribbon as a source of fast protons, produced by high-power lasers.
This, and further planned experimental tests of this innovative cryogenic device, named ELISE, will be crucial to assess the advantages and disadvantages of its future implementation at ELI Beamlines in the ELIMAIA beamline. The ELIMAIA beamline will provide proton/ion beams to users coming from different multidisciplinary research fields, with a special emphasis on medical applications and in particular on innovative approaches to cancer therapy. Thus, these results are expected to contribute to the world leading capabilities of the ELI Beamlines facility.
Pure streams of accelerated protons are key for both cancer therapies and experiments in condensed-matter physics. However, targets that are irradiated with high-power lasers often yield proton streams contaminated with carbon and other ions. The original idea driving these experiments is to produce a syringe with a virtual piston to push solid H2 through a nozzle to create a ribbon with a width of 1 mm and a thickness that can be modulated between 20 and 100 μm. Our linearly polarized nanosecond laser is focused on the H2 ribbon in vacuum conditions (10−5 to 10−4 mbar) at cryogenic temperatures (10 K). We recover a collimated stream of protons with energies in the MeV range that is free of any contaminants. Using another laser as a probe beam, we examine the expansion of the hydrogen plasma at 3 billion kelvin a few nanoseconds before and after the arrival of the laser pulse. We show that the population of protons we recover is 3 times larger than the number of protons derived from a CH2 target. Additionally, we measure a laser-proton acceleration efficiency 2 to 3 times higher than that of previous experiments.
For more details you can read the article recently published in the prestigious journal Physical Review X:
https://journals.aps.org/prx/abstract/10.1103/PhysRevX.6.041030
